3 Answers
3

At a microscopic level metal is malleable, and so the edge tends to bend rather than spall or break off. Still, it is probably technically true to a certain extent, and based on many many years of metal knife usage by millions or billions of people through history, completely irrelevant. Whatever effect it may have is vanishingly small.

I had an Uncle Bob once. He passed away from metal shavings from sharpening his knife. One of those statements may be false...
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rfuscaFeb 26 '14 at 19:16

@Chuu: We ask that people only post such claims if they are well-substantiated and reflect a legitimate scientific consensus. I know that you're trying to be helpful, but the vast amount of pseudoscience and outright nonsense floating around is the reason why we have such specific guidelines for food safety questions (and answers). You might consider posting that as a question on Skeptics, that is if you can find a source to justify it as a "notable" claim.
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Aaronut♦Feb 27 '14 at 1:37

That's basically what I thought - we should have seen some bad effects if it was dangerous at all. What got me thinking was connections to, say, asbestos, and that perhaps I should be even more meticulous with cleaning after honing or sharpening.
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NiklasJFeb 27 '14 at 12:06

@NiklasJ we don't discuss health effects on that scale, as these are very hard to prove or disprove and raise much disagreement even among specialists. All we handle is food safety in the sense "if you eat X, is there a non-neglible chance that you end up in hospital tomorrow". If you want to know if there are long-term health effects, you are in the wrong place.
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rumtscho♦Feb 27 '14 at 15:16

Sure, microscopic bits of metal go into your food when you use knives. It's just a bit more iron in your diet. When you consider that the average person eats 100mg of dirt per day the nanograms of metal you eat per year is pretty insignificant.